This invention relates in general to machines for cutting sheet material, and, more particularly, to an improved blade sharpening apparatus for sharpening the cutting edges of a blade on a numerically controlled cutting machine of the type used in cutting pattern pieces from sheet material layups.
The use of numerically controlled cutting machines in the garment, and other industries where fabric cutting is required is well established. Such numerically controlled machinery is capable of cutting large quantities of pattern pieces from layups of sheet material with high speed and accuracy. Cutting programs control the operation of the cutting tool, such as a reciprocating cutting blade, and cause it to translate through the material layup held in a spread condition on a cutting table.
Numerically controlled cutting machinery has been developed which utilizes a vertically reciprocating blade sharpened along both its leading and lower edges. The known machinery, which may be used to cut material with both slicing and chopping action, has proven particularly advantageous for use in cutting tough materials, and for cutting relatively high piles of such materials. However, to maintain the efficiency and speed of such machinery the blade must be consistently maintained in a uniformly sharp condition.
Blade sharpening apparatus and methods of sharpening have been available for sharpening both the leading and lower edges of reciprocating cutting blades on cutting machines of the aforedescribed general type. Typical blade sharpeners which utilize known methods of sharpening are illustrated and described in my U.S. Pat. Nos. 4,294,047, issued October 13, 1984, and 4,033,214, issued July 5, 1977, and both assigned to the assignee of the present invention, and in U.S. Pat. No. 3,507,177, to Baldwin.
The known cutting machines generally comprise a reciprocating cutting blade suspended from a platform for rotation about an axis perpendicular to the material layup support surface. A blade sharpening apparatus is also suspended from the cutting platform for rotation with the blade about the perpendicular axis, and comprises a sharpening wheel for engagement with the confronting side of the cutting edge of the blade. The sharpening wheel is mounted for rotation on a shaft and has an abrasive surface arranged adjacent the cutting edge of the blade. When the sharpening wheel is precisely aligned with the cutting blade, there is complete surface contact between the abrasive surface and the cutting edge of the blade during sharpening engagement, and therefore effective sharpening occurs. However, only single point or zero contact between the grinding surface and the cutting edge of the blade is maintained if there is not precise alignment, which may be caused by a misaligned wheel, shaft or skewed cutting blade. This condition permits only a limited length of the cutting edge of the blade to be sharpened, at least until a portion of the cutting edge or abrasive surface becomes deformed to allow complete surface contact.
In order to control this undesirable condition, the blade sharpness must be adjusted frequently to maintain consistently precise sharpening wheel and blade alignment for effective sharpening. As a result, the known blade sharpeners have proven to be relatively costly and inefficient in operation.
It is accordingly a general object of the present invention therefore to provide an improved blade sharpening apparatus for sharpening the cutting edges of a blade on a cutting machine without the drawbacks and disadvantages of known blade sharpening apparatus.